Aromatic acid monomers, polymers, products and processes for their manufacture

ABSTRACT

Processes for producing aromatic monomers useful for forming polyesters are disclosed. Cost effective steps employed in the processes permit small amounts of process-related materials typically removed from monomer to remain in an aromatic monomer product. In many cases, the presence of the process-related materials left in the monomer product by the cost effective process steps can enhance the performance of the monomer in certain applications. Aromatic monomer products and polymers produced therefrom having these advantages also are disclosed, as well as products such as pasteurizable bottles made from these polymers

RELATED APPLICATIONS

This is a division of application Ser. No. 09/412,458 filed Oct. 4,1999, now U.S. Pat. No. 6,284,920.

This application claims the benefit of U.S. Provisional PatentApplication No. 60/138,344, entitled “Aromatic Acid Monomers, Polymers,Products and Processes for Their Manufacture”, filed Jun. 9, 1999, andU.S. Provisional Patent Application No. 60/103,393, entitled “AromaticAcid Monomers, Polymers, Products and Processes for Their Manufacture”,filed Oct. 7, 1998.

FIELD OF THE INVENTION

The invention generally relates to polymers formed from aromatic acids.More particularly, the invention relates to aromatic acid monomers whichcontain small amounts of materials that can provide unexpectedadvantages during the polymerization or copolymerization of those acidmonomers, as well as to processes for manufacturing such aromatic acidmonomers and polymers.

BACKGROUND OF THE INVENTION

The manufacture of aromatic acids useful as monomers typically is acomplex, multistep process. For example, 2,6-naphthalenedicarboxylicacid (2,6-NDA) can be manufactured by a five step synthesis processwhich includes the steps of reacting o-xylene and butadiene in analkenylation reaction to produce 5-ortho-tolylpentene, cyclizing the5-ortho-tolylpentene to form 1,5-dimethyltetralin (1,5-DMT),dehydrogenating the 1,5-DMT to produce 1,5-dimethylnaphthalene(1,5-DMN), isomerizing the 1,5-DMN to produce 2,6-dimethylnaphthalene(2,6-DMN), and oxidizing the 2,6-DMN to produce 2,6-NDA.

Crude NDA produced by such a process will contain a wide variety of whatare believed to be undesired process-related materials. Many of thesematerials will be isomers of 2,6-NDA or mono- or trifunctional reactionproducts. Other undesired process-related materials contained in thecrude NDA will be reagents such as catalyst metals carried through thevarious reactions steps, and color bodies formed during the reactionsteps. As used herein, the term “process-related material” means anymaterial that is formed or added in any process step leading up to themanufacture of aromatic acid monomer product, including but not limitedto, catalysts, products of side reactions, undesired oxidation products,undesired isomers and the like.

It is believed that in the preparation of polyesters from monomers suchas NDA, monomer purity is critical to satisfactorily achieving highmolecular weight polymers and a sufficiently fast kinetic rate ofpolymerization. For this reason, polymer manufacturers typically requirethat monomer impurities such as mono-functional and tri-functionalglycols and carboxylic acids be minimized or eliminated from monomers tobe used in polymerization reactions. For example, terephthalic acid andisophthalic acid typically are expected to contain less than 200 partsper million or less by weight total of monocarboxylic and tricarboxylicacids. Similarly, ethylene glycol used in polymerization reactionstypically is expected to contain no detectable impurities.

Tricarboxylic acids are thought to be undesirable because suchtrifunctional compounds can cause undesired cross-linking of polymerchains. Such cross-linking is reported to contribute to slow rates ofcrystallization and polymer brittleness, both of which are undesiredcharacteristics in many applications. Additionally, when cross-linkingbecomes substantial, a “gel point” is reached. At this point, thepolymer cannot be melt polymerized or melt fabricated and is no longerconsidered to be a thermoplastic material.

Monocarboxylic acids and other monofunctional materials are believed tobe undesirable components in monomers because they act as“chain-stoppers” which inhibit the development of molecular weight andbecause they decrease reaction kinetics. If the concentration of suchmaterials is too high, the polymerization rate can become zero due totermination of otherwise reactive end-groups.

Color bodies of various types are thought to be undesirable in monomers.The presence of color bodies in monomer can result in substantiallygreater color in a polymer than would appear likely from seemingly smallamounts of color visible in a monomer, thus making even minute amountsof color bodies in monomers undesirable. As used herein, the term “colorbodies” refers to any carboxylic acid containing process-relatedmaterial present in a monomer or polymer that can contribute to thepresence of color in the monomer or polymer if present in sufficientamount.

Metals such as entrained catalyst metals also are thought to beundesirable components in monomers. For example, entrained cobalt andmanganese oxidation catalyst are believed to be undesirable monomerimpurities because it is expected that they may affect the rate ofpolymerization and polymer color in an unpredictable way. Such metalsalso are thought to sometimes affect the amount of color visible in amonomer or polymer.

Because it is believed that the presence in monomer of undesiredprocess-related materials such as byproducts, reagents and impuritieslike color bodies can result in an inferior polymer product, substantialeffort typically is devoted to improving the purity of monomers such as2,6 NDA to provide a quality of product deemed acceptable by customers.

For example, purified aromatic acids have been produced from crudearomatic acids by slurrying the effluent from a crude aromatic acidoxidation process, passing the slurry through a plurality of heatersuntil the reaction products are dissolved, passing the resultingsolution over a purification catalyst, and thereafter crystallizing apurified product. Such a process requires substantial time and energybeyond that expended to produce crude aromatic acid, and thereforesubstantially increases the cost of the monomer.

Alternatively, high purity monomer can be manufactured by starting witha relatively high purity feedstock, such as a process in whichrelatively pure 2,6-naphthalenedicarboxylate (2,6-NDC) is hydrolyzed toform relatively pure NDA. This process also is cost intensive because ofthe complexity and expense of producing the relatively pure NDCfeedstock.

What is needed is a cost effective way to produce aromatic acids such asNDA which are suitable for use in polymer applications.

SUMMARY OF THE INVENTION

Surprisingly, we have found that the presence of certain levels ofprocess-related materials in aromatic acid monomers can result inmonomers that perform as well as or better than higher purity aromaticacid monomers when used in many polymer applications.

In some applications, the presence of certain levels of catalyst metalscan result in more rapid polycondensation and solid state polymerizationreactions, thereby improving the economics of these polymerizationreactions without affecting the desired properties of the polymerproduct.

In other applications, the presence of certain trifunctional materialsin the aromatic acid monomer product provide for branching of polymerchains, thereby providing increased melt strength which is useful whenmolding articles from the polymer.

In still other applications, the presence of certain levels of metallicimpurities and color bodies provides for an aromatic acid monomer thathas a brownish cast that is useful in particular end uses, including butnot limited to the packaging of drinks such as beer in brown polymerbottles.

While in some cases the foregoing aromatic acid monomers might beproduced directly as solids separated from the product of an oxidationreaction, typically aromatic monomer product in accordance with thepresent invention will be produced by relatively simple post-processingof oxidized aromatic feedstocks, such as by slurrying or washing crudearomatic acid in an appropriate solvent under the appropriate processconditions. Monomer product manufactured in this way can be both lessexpensive and advantageous in certain end uses.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description of preferred embodiments of ourinvention focuses on the advantages of our invention with respect to thepreparation of 2,6 naphthalenedicarboxylic acid monomer product andpolymers made therefrom. As will be discussed later in more detail, theadvantages of the invention also are believed to be useful in connectionwith other aromatic acid monomers such as terephthalic acid, isophthalicacid and other isomers of naphthalenedicarboxylic acids.

As noted above, 2,6-naphthalenedicarboxylic acid (2,6-NDA) can bemanufactured by a five step synthesis process which includes the stepsof reacting o-xylene and butadiene in an alkenylation reaction toproduce 5-ortho-tolylpentene, cyclizing the 5-ortho-tolylpentene to form1,5-dimethyltetralin (1,5-DMT), dehydrogenating the 1,5-DMT to produce1,5-dimethyinaphthalene (1,5-DMN), isomerizing the 1,5-DMN to produce2,6-dimethylnaphthalene (2,6-DMN), and oxidizing the 2,6-DMN to produce2,6-NDA. Aromatic feedstocks such as the 2,6-DMN oxidized in thisprocess preferably contain at least 97 mole percent of the feed materialwhich is to be oxidized to the acid, calculated as a mole percent of allaromatic material in the feedstock.

Crude 2,6-NDA produced by the foregoing process preferably contains atleast 93 mole percent acid monomer and typically is expected to containunacceptable levels of one or more of the following materials:trifunctional materials, 1-bromo-2,6-NDA, 2-naphthoic acid,6-formyl-2-naphthoic acid, cobalt, manganese, bromine, iron and variouscolor bodies. We have found that it frequently is not harmful, and inmany cases it is advantageous, to permit certain levels of metals,tri-functional compounds, and color bodies to be present in 2,6-NDAmonomer product used in polymerization reactions. In many cases, theseacceptable and advantageous material levels can be obtained byrelatively simple processing of the oxidation product of 2,6-DMN,thereby eliminating the need for costly purification steps such asrecrystallization.

Acceptable and preferred levels of the foregoing materials consistentwith our invention are listed in Table 1, below. The ppm ranges listedrefer to ppm by weight of the material present in NDA monomer product.

TABLE 1 Material Acceptable level Preferred Level trifunctionals 50 to10,000 150 to 8,500 monofunctionals 50 to 5,000  150 to 3,500 metals(Co + Mn) 50 to 10,000 500 to 2,000 color bodies 50 to 500   50 to 250 

NDA monomer having one or more of the foregoing materials inconcentrations in accordance with our invention readily can be produced,for example, by slurrying crude NDA oxidation product to remove afraction of such materials, while permitting a desirable, or at leastnon-deleterious, portion of such materials to remain in the monomer. Asused herein, the term “slurry” refers to any process which employs asolvent to wash or disperse a crude oxidation product, but specificallyexcludes any process which dissolves greater than about 10 mole percentof a desired aromatic monomer present in crude oxidation product, suchas a recrystallization step. Other examples of “slurry” processes inaccordance with the invention include the use of higher solvent volumesin the reactor in which the aromatic feedstock is oxidized to render theprocess-related materials more soluble, thereby somewhat reducing thelevels present in the product, adding or increasing the volume ofsolvent in the crystallizer train of the oxidation process to reduce thepresence of process-related material by dilution, and the use offiltration with a solvent wash to reduce the level of process-relatedmaterials remaining in the monomer product.

For example, crude 2,6-naphthalenedicarboxylic acid can be recovereddirectly from 2,6-DMN oxidation mother liquor. The crude 2,6-NDA thencan be redispersed or reslurried in a suitable solvent such as water, alow molecular weight carboxylic acid, or a mixture of water and a lowmolecular weight carboxylic acid at a weight ratio of about 0.1 to about1 part of 2,6-naphthalene dicarboxylic acid per part of solvent.Preferred process conditions for the reslurry process includetemperatures of from 60 to 125° C., with 75 to 110° C. being mostpreferred, and pressures of from about 0.5 to 3 atmospheres, withpressures from 1 to 2 atmospheres being most preferred. Solvent acid towater ratios can range from 100 percent acid to 100 percent water, withthe preferred acid to water part ratio being from about to 90:10 to50:50, with the most preferred ranges being about 80 parts acid and 20parts water.

Preferably, at least a portion of the solvent used to redisperse orreslurry the 2,6-naphthalene dicarboxylic acid in this manner is aprocess stream or process-derived stream such as condensate from theoverhead of the oxidation reaction mixture. In this case, solventcomprising water and an acid such as acetic acid can be returned, atleast in part, to the oxidation reactor. Alternatively, the solvent canbe distilled to recover the low molecular weight carboxylic acid forrecycle to the oxidation reactor. Solvents may contain other processmaterials that will not substantially affect the slurry process orproperties of the monomer product, such as alcohols or acetatesgenerated in the process. Such process streams should, however, containlittle or none of the process-related materials sought to be minimizedin the slurry process.

The foregoing slurry step provides for a relatively purer2,6-naphthalenedicarboxylic acid. In many cases, such a 2,6-NDA monomerproduct in accordance with the invention will be suitable or preferredfor certain applications over a monomer product produced from a morecomplex process having additional purification steps.

After this slurry step, the 2,6-naphthalenedicarboxylic acid can beseparated from the solvent by any method or methods known in the art forpartitioning a solid from a liquid phase such as, for example,centrifugation, filtration, or settling.

Of particular interest in the reslurried NDA are the concentrations ofcatalyst metals such as cobalt and manganese, the ratio of cobalt andmanganese metals, the level of multifunctional aromatic compounds, andthe level of colored impurities.

The levels and ratios of catalytic metals are important both becausethey will affect the polymerization rate of the monomer and becausetheir presence may, in some cases, influence the final polymer color.For NDA applications, the total amount of Co and Mn present in thereslurried material should be no more than about 10,000 ppm by weight inthe reslurried product, with 500 to 2,000 ppm being preferred, and 1000to 1,500 ppm being most preferred. The molar ratio of Co to Mn can rangefrom 5:1 to 0.2:1, with the preferred ratios being between 4:1 to0.25:1, and the most preferred ratios being between 3:1 and 0.5:1.

The levels of multifunctional materials are important when the polymerto be produced from the aromatic monomer requires additional meltstrength. For NDA applications, trifunctional naphthalenic moieties arethe more likely species, with 1,2,6-, 1,3,7- and 2,3,6- naphthalenetricarboxylic acids predominating in the mix. Preferably, thesetrifunctional species will be present in the reslurried NDA in an amountbetween 50 and about 10,000 ppm by weight, preferably between about 200and 9,000 ppm by weight, and most preferably between about 150 and 8,500ppm by weight. When other aromatic monomers such as PTA are the subjectof the invention, trifunctional acids such as 1,2,3-, 1,2,4- and1,3,5-benzene tricarboxylic acids, and mixtures thereof are the morelikely trifunctional species, and may be present in the ranges set forthabove for the napthalenic trifunctional species. Mixtures of any and allof the foregoing trifunctional impurities may, of course, be present inaccordance with the invention, and impurities having a functionalitygreater than 3 may also be advantageously utilized in accordance withthe invention. As used herein, the term “trifunctional material” meansany process-related material having three functional groups capable ofreacting with a glycol monomer under polymerization conditions. The term“multifunctional material” means any such material with a functionalityof three or more.

Polyester color is a very important performance requirement in certainapplications, while in other applications, color is not important.Sometimes, a color such as brown is required for certain packagingapplications. The brown color typically is achieved by the addition ofdyes which usually are high molecular weight organic compounds. Dyes areundesirable because they can detract from the polyester properties,especially barrier permeation to gases such as oxygen and carbondioxide. Additionally, dyes are expensive, and can be undesirable fromenvironmental and recycling standpoints. Thus, color bodies present inan aromatic acid monomer may be useful for inducing a color such asbrown into subsequently formed polymers. Color bodies useful inaccordance with the invention include benzcoumarin, pentaquinone,pentacene and flourenone structures containing carboxylic acidfunctions. Typically, these color bodies should be present in an amountbetween about 50 and about 500 ppm by weight, more preferably betweenabout 50 and 250 ppm, and most preferably present at a level of about150 ppm.

Slurried NDA in accordance with the invention also can containmonofunctional impurities including, but not limited to, such aromaticacid impurities as benzoic acid and benzoic acid substituted with groupssuch as methyl, bromo, and formyl groups, as well as 1- and 2-naphthoicacid and 1- and 2-naphthoic acid substituted with groups such as methyl,bromo, and formyl, and mixtures thereof. The concentration ofmonocarboxylic acids in a reslurried NDA typically is from about 50 to5,000 ppm by weight, preferably 100 to 4,000 ppm by weight, and mostpreferably about 150 to 3500 ppm by weight. As used herein, the term“monofunctional material” means any process-related material having asingle functional group capable of reacting with a glycol monomer undertypical polymerization conditions.

Each of the foregoing materials need not be present in the amountsmentioned above if the desired advantage attributable to that materialis not required in the desired monomer application.

By way of example, the crude NDA can be reslurried to yield an NDAmonomer having the approximate specifications set forth in Table 2,below.

TABLE 2 Material Level trifunctionals 5,500 +/− 1,500 ppmmonofunctionals 2,000 +/− 1,000 ppm metals (Co + Mn) 1000 +/− 500 ppm color bodies 150 +/− 120 ppm

Examples 1 and 2, below, demonstrate the effect of cobalt and manganesemetal on the rate of polymerization of an aromatic polymer. The effectof catalytic metals in NDA monomer in a purified terephthalic acid(PTA)/naphthalenedicarboxylic acid (NDA) polymer was demonstrated bycomparing the polymerization of an antimony-catalyzed 92 mole percentPTA/8 mole percent NDA mixture polymerized with ethylene glycol (thepolymer being hereafter referred to as “PETN-8”) with that of a similarmixture that had been “spiked” with 90 ppm by weight of cobalt (ascobalt acetate) and 30 ppm by weight of manganese (as manganeseacetate). The polymerization times for both mixtures were measured forpressure esterification, atmospheric esterification and polycondensationreactions.

EXAMPLE 1

In this example, the melt polymerization of PETN-8 without cobalt andmanganese concentrations in the range of the invention was demonstrated.The following materials were placed into a 56-liter, helical-agitatedreactor: 12.86 kg of ethylene glycol, 27.53 kg of terephthalic acid,3.12 kg of 2,6-naphthalene dicarboxylic acid, 1.34 grams oftetramethylammonium hydroxide, 8.46 grams of antimony trioxide, and 3.00grams of cobalt acetate (20 ppm based on polymer yield). The initialreactor temperature was 107° C. and the reactor was pressurized with 40psig nitrogen pressure. The melt temperature was increased to 223-246°C. and water was removed while the pressure was maintained at 40 psig.When water evolution stopped, the pressure was reduced to atmosphericand pressure esterification was completed. The pressure esterificationtime was 218 minutes.

The melt temperature then was increased to 263° C. and atmosphericesterification was continued for 60 minutes. An additional 100 grams ofethylene glycol and 3.83 grams of phosphoric acid were added. Thereactor pressure was decreased from atmospheric to 3 mm Hg over a periodof 65 minutes as the melt temperature was increased to 285° C. Meltpolycondensation was continued for an additional 108 minutes for a totalof 173 minutes of polycondensation time to reach an agitator torquevalue of 1800 pound-inches. The product was stranded, quenched, andpelletized. The product had an inherent viscosity of 0.58 dL/g measuredin 60/40 phenol/tetrachloroethane at 30° C. and a concentration of 0.4g/dL.

EXAMPLE 2

The following example demonstrates the melt polymerization of PETN-8with cobalt and manganese concentrations present in the range of theinvention. Example 1 was repeated with the same raw materials andweights except that 4.42 grams (28 ppm based on polyester weight) ofmanganese acetate was added and the amount of cobalt acetate added was13.59 grams (91 ppm based on polyester weight). Using identicaltemperatures and pressures, the pressure esterification time was 220minutes. The atmospheric esterification time was 60 minutes and thepolycondensation time at the 285° C. melt temperature required to obtain1800 pound-inches of torque was 117 minutes. The product's inherentviscosity was 0.59 dL/g.

As can be seen by comparing Examples 1 and 2, the pressure andatmospheric pressure esterification reactions were completed in about220 and 60 minutes respectively for both the “spiked” and controlsamples of Examples 1 and 2. Beneficially, however, the polycondensationreaction of the “spiked” sample was completed in about 117 minutes, ascompared to about 173 minutes for the control sample. The substantialreduction in reaction time is believed to provide a major economicadvantage in use.

Example 3, below, demonstrates that the presence of mono- andtricarboxylic acid impurities does not adversely effect the meltpolymerization of PETN-8.

EXAMPLE 3

Example 1 was repeated with the same raw materials and weights as thecontrol except that 12.57 grams of trimellitic acid, 3.80 grams of2-formyl-6-naphthoic acid, 2.22 grams of 2-naphthoic acid, and 0.19grams of 2-methyl-6-naphthoic acid were added. High purity NDA obtainedby the hydrolysis of NDC was used in the control, while reslurried crudeNDA obtained directly from an oxidation of DMN was used in the sample inaccordance with the invention. The composition and characteristics ofthe control and the mono- and trifunctional-containing sample are setforth below. Color bodies were present in the crude sample but were notquantified.

Control Invention Impurity (ppm) Tricarboxylic Acids None 4,029Monocarboxylic Acids 109 1,993 Catalyst Level (ppm) Cobalt 20 90Manganese None 30 Antimony 200 200 Process Time (Minutes) PressureEsterification 218 215 Atmospheric Esterification 60 60 Polycondensation173 118 Polyester Properties Inherent Viscosity, dL/g 0.58 0.56 Color,*b value 0.38 +14.62

The reduction in polycondensation time from 173 minutes to 118 minutesin accordance with the present invention is believed to be of majoreconomic significance.

With respect to color, it should be noted that the *b color value notedabove is a tristimulous color value on the blue/yellow scale. On thisscale, a negative value appears blue and a positive value appearsyellow, but with *b values greater than about +10, the visual appearanceis brown. Therefore, the polyester prepared according to the inventionparticularly was suitable for beer bottle and other brown containerapplications without the added cost and environmental concern of theaddition of an organic dye or pigment. Such color body-containingpolyesters of this invention also are useful as relatively low costpolyesters in applications where white color is not a requirement, suchas for industrial fibers and insulating films.

Example 4, below, illustrates the increased ability of polymers inaccordance with the invention to polymerize in the solid state.

EXAMPLE 4

3.0 gram polymer pellets produced from the materials of Examples 1 and 2were crystallized in an oven at 150° C. for 2.0 hours. The pellets wereplaced in test tubes, vacuum was applied, and the test tubes placed inan oil bath at room temperature. The oil was heated over a period of 200minutes to 410° F. which was considered the starting point for solidstate polymerization. Samples were periodically removed from the oilbath and the following data obtained:

Inherent Viscosity (dL/g) Time (Hours) Control Invention Start 0.60 0.551.0 0.61 0.62 2.0 0.62 0.64 4.0 0.65 0.68 6.0 0.71 0.73 8.0 0.75 0.77Rate (dL/g) 0.0188 0.0238

The foregoing data demonstrates an approximately 40 percent solid statepolymerization rate increase for the invention compared to the control.

Examples 5 and 6, below, demonstrate that films can be formed andstretched from polymers in accordance with the invention, and that thepresence of extraneous material in the polymer does not adversely affectthe film product.

EXAMPLE 5

Solid state polymerized pellets in accordance with the invention fromExample 4 were dried for 16 hours at 150° C. and melt extruded using aKillion Model KL-125 single screw extruder equipped with a 1.25 inchscrew with a length to diameter ratio of 24 to 1 (L/D=24/1). Theextruder was equipped with a six inch adjustable lip sheet die and threechilled temperature rolls for take-off. A heater temperature profile of515/525/530/530/530/500° F. (feed throat to die) was employed and thescrew speed was 75 rpm. High quality, amorphous sheet having a thicknessof approximately 23 mils was produced.

EXAMPLE 6

Samples of the sheet from Example 6 were biaxially oriented in a T. M.Long stretcher. The samples were heated to 226-244° F. for a period of2.0 minutes and stretched at a stain rate of approximately 300%/secondto produce 3×3 biaxially oriented films.

The following film properties were measured:

Property Control Invention Crystallinity, % 25.0 23.7 Carbon DioxidePermeation 34.2 31.2 (cc-mil/100 in 2-day-atm @ 35° C.)

As can be seen from the foregoing data, the PETN-8 copolyester sample ofthe invention which contained high levels of moncarboxylic acids andtricarboxylic acids exhibited essentially the same level ofcrystallinity as the control sample and both films had similar carbondioxide permeation values. However, the lower permeation value for theinvention translates into longer shelf-life for packaging applications.Both films were very tough and showed no evidence of brittleness.

Other preferred polyesters which can employ NDA monomer product inaccordance with the present invention include any PTA/NDA polymer havingmolar ratios of PTA to NDA of 99:1 to 0:100. Preferred ranges of NDA toPTA in NDA/PTA polyesters will range from 2 to 15 mole percent NDA to 98to 85 mole percent PTA, with 2 to 9 mole percent NDA to 98 to 91 molepercent PTA being more preferred. NDAs useful in the invention can beany polymerizable isomer such as 2,6-, 1,5-,1,4- and 2,7-NDA, as well asmixtures thereof. The polyesters also can include up to about 15 molepercent of other carboxylic acids such as isophthalic acid and/or adipicacid. The polyester also may incorporate up to about ten mole percent ofa glycol such as diethylene glycol, 1,4-butanediol, polybutadiene glycolor 1,4-cyclohexanedimethanol, or mixtures thereof. With respect to theranges of process-related materials set forth in Table 1, above, itshould be noted that higher levels of monomer impurities a re preferredin monomer product intended to be used as small fractions of acopolymer, while lower levels of impurities will be preferred where themonomer product comprises large fractions of a copolymer or where theend product is a homopolymer.

The inherent viscosity of polyesters in accordance with the presentinvention as measured in a 60/40 solution of phenol/tetrachloroethane at30° C. and a concentration of 0.4 grams/dL typically will be betweenabout 0.40 to 1.00 dL/gram, preferably about 0.50-0.90 dL/g, and mostpreferably between about 0.60-0.80 dL/g.

The dicarboxylic acid component of polyesters in accordance with theinvention optionally may be modified with up to 15 mole percent of oneor more different dicarboxylic acid s other than terephthalic acid and2,6-naphthalenedicarboxylic acid. Such additional dicarboxylic acidsinclude aromatic dicarboxylic acids preferably having 8 to 14 carbonatoms, aliphatic dicarboxylic acids preferably having 4 to 12 carbonatoms, or cycloaliphatic dicarboxylic acids preferably having 8 to 12carbon atoms. Examples of dicarboxylic acids to be included are phthalicacid, isophthalic acid, cyclohexanediacetic acid,4,4′-biphenyldicarboxylic acid, succinic acid, glutaric acid, adipicacid, fumaric acid, azelaic acid, sebacic acid,1,4-cyclohexanedicarboxylic acid, resorcinoldiacetic acid, diglycolicacid, 4,4-oxybis(benzoic) acid, 1,12-dodecanedicarboxylic acid,4,4′-sulfonyldibenzoic acid, 4,4′-methylenedibenzoic acid, trans4,4′stilbenedicarboxylic acid, 2,6-dicarboxytetralin,2,6-dicarboxydecalin, and the like.

Other additives and stabilizers known in the art such as glass fibers,mineral reinforcement, oxygen scavengers, diethylene glycolsuppressants, optical brightening agents and phosphorous-containingstabilizers can be incorporated into monomer product or polymers madetherefrom in accordance with the invention.

Monomers in accordance with the invention also may be used to producehomopolymers and copolymers from relatively pure acids by adding thematerials described herein in the amounts set forth herein.

For example, metal salts particularly useful for preparingmetal-containing monomers include cobalt and manganese alkylates such asacetates, halides, especially bromides, and organic acid salts,particularly aromatic salts. When adding salts to relatively purearomatic acids, metal concentrations can range from about 20 to 10,000ppm by weight, more preferably between about 50 to 2000 ppm by weight,and most preferably between about 100-1000 ppm by weight.

If Co and Mn are added to produce a monomer in accordance with theinvention, the molar ratio of Co to Mn can range from 5:1 to 0.2:1, withthe preferred ratios being between 4:1 to 0.25:1, and the most preferredratios being between 3:1 and 0.5:1.

Polymers in accordance with the invention can be produced in the samemanner as polymers are produced from purer monomers of the same acids.Such polymerization reactions are well-known in the art. See, forexample, The Encyclopedia of Chemical Technology, Vol. 18, pp. 531-594,John Wiley and Sons (1982), the disclosure of which is herebyincorporated by reference.

Co- and homopolyesters produced in accordance with the invention can beused to manufacture sheets and biaxially oriented films, fibers, stretchblow molded containers and any other application where such polyesterstypically are employed. See, for example, Plastics Engineering Handbook,4th Edition, Van Nostrand Reinhold Company (1976), the disclosure ofwhich is hereby incorporated by reference.

The presence of metals, color bodies and other impurities in the acidmonomer of the present invention make these monomers particularly usefulin NDA-copolymer applications where the presence of color is desired ornot objectionable, as well as where enhanced high temperatureperformance is required. Typical applications particularly suitable foruse of copolymers in accordance with the invention are containers forfood or beverages that require heating or pasteurization and which mustexhibit dimensional stability during and after the heating orpasteurization process. This is especially true where the packagedmaterial contains carbon dioxide or another gas which will generatesubstantial internal package pressure when heated. Specific examples ofsuch applications are pasteurizable bottles for beer, and bottles forfruit juices such as prune juice, where package heatability and colorare desired package characteristics. The utility of NDA/PTA copolymersis demonstrated by Example 7 below.

EXAMPLE 7

One half liter capacity, long neck, pasteurizable amber beer bottleshaving a champagne base were fabricated from experimental copolymerscontaining reslurried acid monomer in accordance with the compositiondescribed in Table 2, above.

In Example 7A, the PETN-3 copolymer employed contained 3 mole percent ofthe reslurried NDA and 97 mole percent of a purified terephthalic. Inthis Example, a 35.0 gram injection molding preform was prepared. Thepreform contained approximately 15 grams of copolymer in the shoulderarea, about 10 grams of copolymer in the panel area, and about 10 gramsof material in the base area.

In Example 7B, a PETN-5 copolymer contained 5 mole percent of thereslurried NDA and 95 mole percent of the same purified terephthalicacid. In this Example, a 34.1 gram injection molding preform wasprepared. The preform contained approximately 14.7 grams of copolymer inthe shoulder area, about 10 grams of copolymer in the panel area, andabout 9.4 grams of material in the base area.

The preforms of Examples 7A and 7B were blown into 0.5 liter bottlesusing a Sidel SBL2/3 stretch blow molding machine. Carbonated watercontaining about 2.9 to 3.1 volumes of carbon dioxide was added to eachbottle to a predetermined fill line and capped.

The capped bottles were placed in a pasteurization chamber and sprayedwith 71 degree Centigrade water until the bottle contents reached atemperature of about 63° C. The spray water temperature was then reducedto 64° C. to maintain the bottle contents at 63° C. for an additional 15minutes. Spray water temperature was then reduced until the bottlecontents reached 40° C., after which time the bottles were chilled toroom temperature in a cold water bath.

Several physical parameters of the pasteurized bottles were measured todetermine the effects on the bottles from the pasteurization process.The results of those measurements are summarized in Table 3 below.

TABLE 3 Bottle material PETN-3 PETN-5 Resin IV 0.80 0.80 DimensionalChanges (% increase) Height 0.43 0.26 Diameter Upper Bumper 1.94 2.15Mid Panel 1.74 0.48 Lower Bumper 1.03 1.04 Neck 1.27 1.36 Fill Line Drop(in.) 0.60 0.69 Perpendicularity (in. off 0.119 0.152 bottle centerline) Pressure (volumes) 2.71 2.68

In the case of Examples 7A and 7B, both bottles' dimensional changeswere judged acceptable based on pressure retention (at least 75% of theprepasteurization pressure was retained when initially charged to apressure of about 3 volumes), and perpendicularity (deviation from thevertical less than 0.25 inches for the vertical radial axis of bottlesymetry when the pasteurized bottle is standing on its base, with thedeviation measured at the top of the bottle. Fill line drops of lessthan 3 percent also are preferred.

It was also found that injection blow molding bottle preforms containingbetween about 40-46 weight percent of their material in the shoulderregion, 26-32 weight percent of their material in their panel region and25-31 weight percent of their material in the base region were mostsuccessful in withstanding the pasteurization tests. These approximatepreform weight distributions and geometries are believed to be usefulfor half liter bottles formed from other polymers and are believed to bescalable for producing pasteurizable bottles of other volumes.

While the foregoing examples describe the invention with respect tocertain naphthalenic acid monomer products, those of ordinary skill inthe art will recognize that the invention is equally useful inconnection with monomers such as terephthalic acid, isophthalic acid andthe like, with process-related materials present in approximately thesame ranges when corrected for the molecular weight difference betweennaphthalenic and other aromatic monomers. Additionally, when monomersaccording to the present invention are used to make copolymers, theprocess-related materials present in accordance with the presentinvention may be present, for example, in any one monomer, or in morethan one monomer. For these reasons, our invention is intended to belimited only by the scope of the following claims.

We claim:
 1. A process for producing a naphthalenic dicarboxylic acidmonomer product suitable for the manufacture of polyesters, said processcomprising the steps of: oxidizing a naphthalenic feedstock to produce acrude naphthalenic dicarboxylic acid; processing the crude naphthalenicdicarboxylic acid to produce a naphthalenic dicarboxylic acid monomerproduct comprising at least 90 mole percent of the acid monomer and oneor more process-related materials selected from the group consisting ofbetween 50 and 5,000 ppm of monofunctional materials, between 50 and10,000 ppm of trifunctional materials, between 50 and 500 ppm of colorbodies, and between 50 and 10,000 ppm of metals; wherein the processingstep includes slurrying the crude naphthalenic dicarboxylic acid in asolvent selected from the group consisting of water, aliphatic organicacids having between 2 and 4 carbon atoms, and mixtures thereof.
 2. Theprocess of claim 1 wherein the processing step includes slurrying thecrude naphthalenic dicarboxylic acid in a solvent selected from the,group consisting of water, aliphatic organic acids having between 2 and4 carbon atoms, and mixtures thereof.
 3. The process of claim 2 whereinthe slurrying step is performed at a temperature of about 60 to 125° C.,at a pressure of from about 0.5 to 3 atmospheres, and at a solvent tocrude naphthalenic acid weight ratio of about 0.5:1 to 20:1.
 4. Theprocess of claim 2 wherein the slurrying step is performed at atemperature of about 75 to 110° C., at a pressure of from about 1 to 2atmospheres, wherein the solvent comprises at least 50 mole percentacetic acid, and at a solvent to crude naphthalenic acid weight ratio ofabout 1:1 to 10:1.
 5. The process of claim 1 further comprising the stepof producing a homopolymer or copolymer article from monomers comprisingthe naphthalenic dicarboxylic acid monomer product, said article beingselected from the group consisting of sheets, films, oriented films,fibers, injection molded articles, and blow molded articles.
 6. Theprocess of claim 1 wherein the copolymer is formed from monomerscomprising between about 2 and 15 mole percent of the naphthalenicdicarboxylic acid monomer product and from between about 98 and 85 molepercent of one or more aromatic acids selected from the group consistingof terephthalic acid, isophthalic acid, and adipic acid, and mixturesthereof.
 7. The process of claim 1 wherein the copolymer is formed frommonomers comprising between about 2 and 9 mole percent of thenaphthalenic dicarboxylic acid monomer product and from between about 91and 98 mole percent of terephthalic acid.
 8. A polyester comprising atleast 2 mole percent of a naphthalenic dicarboxylic acid monomer producthaving between about 50 to 250 ppm of color bodies and a tristimuluscolor value of greater than +10 on a yellow/blue scale wherein saidnaphthalenic dicarboxylic acid monomer product is produced by theprocess of: oxidizing a naphthalenic feedstock to produce a crudenaphthalenic dicarboxylic acid; processing the crude naphthalenicdicarboxylic acid to produce a naphthalenic dicarboxylic acid monomerproduct comprising at least 90 mole percent of the acid monomer and oneor more process-related materials selected from the group consisting ofbetween 50 and 5,000 ppm of monofunctional materials, between 50 and10,000 ppm of trifunctional materials, between 50 and 500 ppm of colorbodies, and between 50 and 10,000 ppm of metals.
 9. A copolymer formedfrom monomers comprising between about 2 and 10 mole percent of apolymerized naphthalenic dicarboxylic acid monomer product and frombetween about 98 and 91 mole percent of terephthalic acid wherein; saidpolymerized naphthalenic dicarboxylic acid monomer product comprises atleast 90 mole percent of the acid monomer and one or more materialsselected from the group consisting of between 50 and 5,000 ppm ofmonofunctional materials, between 50 and 10,000 ppm of trifunctionalmaterials, between 50 and 500 ppm of color bodies, and between 50 and10,000 ppm of metals, and combinations thereof.
 10. An article formedfrom the copolymer of claim 9, said article being selected from thegroup consisting of sheets, films, oriented films, fibers, injectionmolded articles, and blow molded articles.
 11. A process comprising: (a)producing a naphthalenic dicarboxylic acid monomer product by oxidizinga naphthalenic feedstock to produce a crude napthalenic dicarboxylicacid comprising a naphthalenic dicarboxylic acid useful as a monomer ina polymerization reaction and process-related materials formed duringthe manufacture of the crude naphthalenic dicarboxylic acid; slurryingthe crude naphthalenic dicarboxylic acid in a solvent to remove aportion of process-related materials from the crude naphthalenicdicarboxylic acid; recovering solid monomer from the slurry to produce anaphthalenic dicarboxylic acid monomer product comprising at least 93mole percent of the acid monomer and one or more process-relatedmaterials selected from the group consisting of between 50 and 5,000 ppmof monofunctional materials, between 50 and 10,000 ppm of trifunctionalmaterials, between 50 and 500 ppm of color bodies, and between 50 and10,000 ppm of metals; (b) polymerizing the naphthalenic dicarboxylicacid monomer product into a homopolymer or a copolymer without firstperforming an intervening process step intended to remove theprocess-related materials from the monomer product prior to conductingthe polymerization.
 12. The process of claim 11 wherein the copolymer isformed from monomer comprising between about 2 and 9 mole percent of thepolymerized naphthalenic dicarboxylic acid monomer product and frombetween about 98 and 91 mole percent of terephthalic acid.
 13. Theprocess of forming, from the copolymer of claim 12, an article selectedfrom the group consisting of sheets, films, oriented films, fibers,injection molded articles, and blow molded articles.
 14. A pasteurizableblow-molded bottle prepared from a polymerized material comprising acopolymer formed by the process of claim 12, wherein the copolymercontains between about 2 and 9 mole percent of the naphthalenicdicarboxylic acid monomer product and from between about 98 and 90 molepercent of terephthalic acid, said bottle being capable of containing agas-containing liquid during a pasteurization process in which thetemperature of the gas-containing liquid is maintained at a temperatureof at least 60° C. for at least 15 minutes during said process, andwherein said bottle is capable of retaining at least 70 percent of aninitial gas pressure when charged to an initial gas pressure of about 3volumes of gas per bottle volume.
 15. The bottle of claim 14, wherein,after pasteurization, the bottle has a vertical axis of radial symetrythrough the bottle which deviates from perpendicular of less than 0.25inches.
 16. The bottle of claim 14, wherein the bottle is a bottlehaving an approximate 500 milliliter capacity, and wherein the bottle isblown from a preform having a shoulder area, a panel area and a basearea, said areas expanding during the blowing process under exposure toheat and pressure to form a blow molded bottle, and in which theshoulder area contains between about 14 to 16 grams of polymer, whereinthe panel area contains between about 9 to 11 grams of polymer, andwherein the the base contains between about 8.5 and 11 grams of polymer.